1. Field of the Invention
The invention relates to the use of a guitar to control musical tones generated by an electronic musical instrument.
2. Description of the Prior Art
Most of the present generation of electronic musical instruments, such as those known by the generic name of tone "synthesizers" are operated and controlled from a clavier type keyboard. With the employment of a variety of available digital command interfaces for controlling a tone synthesizer, there is really no inherent restriction that the input note data information be provided by a keyboard.
Guitar controllers for interfacing with a tone synthesizer have been implemented by using frequency analyzers which are configured as frequency-to-voltage devices. These provide a control voltage which corresponds to the fundamental frequency of an analog signal produced by the acoustic transducers used to convert the guitar string vibrations to an electrical signal. There are inherent and conflicting limitations in a system employing frequency-to-voltage devices for a guitar controller. A plucked guitar string has a time variant waveshape which can be roughly divided into three time intervals. The first region corresponds to the onset of tone when a string is plucked. This region produces a signal which has a noise-like character. The second time region is a sort of transitional region wherein the noise-like character of the sound starts to diminish and the onset of a musical waveshape having pronounced higher harmonics begins. In the third time region the generated musical waveshape assumes a quasi-steady state in which the harmonics are essentially stable and the strings emit the characteristic guitar tone.
If a frequency-to-voltage conversion device follows the frequency variations of the waveshape with a very fast response time, "glitches" or totally unrecognizable and somewhat objectionable transient tones would be produced by the controlled tone synthesizer in response to the rapidly varying generated control signals. If the response time of the frequency-to-voltage device is slowed down sufficiently so that it does not respond to the first two regions of the plucked guitar string musical waveform then an audible delay will occur between the time the guitar string is plucked and the time at which the controlled tone synthesizer starts to generate as associated tone. This delay time can be both objectionable and distracting to both the guitar player and a listener. A frequency-to-voltage conversion device requires about two to ten cycles of a waveform to determine the pitch of the corresponding note. For a low frequency guitar note such as E.sub.2 which has a frequency of 82.41 Hz, a delay of even two cycles corresponds to a time delay of about 24 milliseconds. This time delay is clearly obvious to the player and listener.